We have evidence that x-ray contrast media are able to produce chromosome aberrations in human lymphocytes. This suggests that the contrast media pose an unsuspected long-term hazard to patients. We propose to determine the contribution of contrast media to chromosome aberrations by measuring the aberrations in peripheral blood lymphocytes obtained from patients before and after angiography and pyelography. We shall compare the aberration frequencies with those expected on the basis of the x-ray exposure--the difference will provide a measure of the contribution of the contrast media. We propose to examine the persistence and possible consequences of chromosome aberrations induced by angiocardiography. Chromosome aberrations will be scored in selected patients who had undergone angiography as young children at times up to twenty years after angiography. We shall document all non-cardiac medical problems in the patients and compare them with controls. We propose to identify the chromosome damaging agents in two widely used injectable contrast media--one, a solution of sodium diatrizoate, the other a solution of sodium diatrizoate and meglumine diatrizoate. We shall examine the cytogenetic effects of inorganic iodide, free aromatic amines, the buffer, and other components in the contrast media on cultures of human lymphocytes and Chinese hamster cells, and in rabbit bone marrow cells. We shall use a multi-parameter cell sorter to measure changes in the DNA, RNA, and protein content per cell in order to quantitate changes in cell kinetics, and we shall use a microscope to measure changes in the frequencies of micronuclei and chromosome aberrations produced by the components in the contrast media.